Global Water Cycle Is Revving Up : Nature News Blog
erhaps the most inconvenient thing about global warming is that mainly the poor will have to carry the can. While, for example, the amount of rainfall at wealthy and relatively freshwater-blessed mid and high latitudes is likely to increase as the climate warms, drought-prone regions such as the Sahel zone will likely get even drier.
Computer models used to simulate the effects of rising global temperature on the climate system at large do predict changes in the global water cycle whereby, metaphorically, the ‘rich get richer’ and the ‘poor get poorer’. An analysis published in the journal Science today of 50 years of ocean salinity data - an excellent indicator of a changing hydrological cycle - finds that existing models strongly underestimate the magnitude of the changes.
The laws of physics - namely vapour pressure dependence on temperature - dictate that a warm atmosphere can hold much more water vapour than a cold atmosphere. As global temperature rises, so will evaporation, atmospheric moisture content and precipitation. At the same time, global atmospheric circulation models suggest that the distribution of rainfall will change along a pattern that will dry subtropical areas and increase precipitation at higher latitudes